hiredis是redis官方推荐的C/C++客户端代码库。使用hiredis库很简易方便的进行redis的相关开发。
同步方式
不过大多数情况下，我们采用的都是同步的调用方式。
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/* 和redis服务器建立TCP连接 */
redisContext *redisConnectWithTimeout(const char *ip, int port, const struct timeval tv);
/* 发送指令到redis服务器，并取得结果 */
void *redisCommand(redisContext *c, const char *format, ...);
/* 处理完结果后，释放内存 */
void freeReplyObject(void *reply);
/* 释放和redis服务器的连接 */
void redisFree(redisContext *c);
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没错，同步的方式就是这么简单易用。
异步方式
不过说到了同步，那必然得说异步。同步简单，异步性能高。为了性能，或者说为了装B，必须得用一下异步调用方式才能显示得出高大上。
当然，本文不是描述基于libevent，或者基于redis本身得ae网络库的异步方式。而是基于公司（或者自己）已有的异步服务器框架上，我们需要：
- 将发送redis的请求按照redis的既有协议打包到一个buffer。
- 将这个buffer丢给异步服务器框架，由框架负责和redis服务器建立（维护）连接，发送请求buffer，并取得redis返回的数据buffer。框架保证这个过程是异步高性能的。
- 然后框架会给出redis的回包buffer。我们需要按照redis的既有协议解开这个包，并得到结果。
redis的既有协议，这里先不展开描述。回到上面的需求，我们怎么才能打包redis的请求，解包redis的返回数据呢？用习惯了同步的方式，还曾经抱怨hiredis为什么不提供一个打包的函数和一个解包的函数呢。原来是自己眼拙，没看出hiredis库的打包和解包的使用方式。
打包函数系列：
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/* Functions to format a command according to the protocol. */
int redisvFormatCommand(char **target, const char *format, va_list ap);
int redisFormatCommand(char **target, const char *format, ...);
int redisFormatCommandArgv(char **target, int argc, const char **argv, const size_t *argvlen);
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解包是通过一个redisReader来完成的。
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/* State for the protocol parser */
typedef struct redisReader {
int err; /* Error flags, 0 when there is no error */
char errstr[128]; /* String representation of error when applicable */
char *buf; /* Read buffer */
size_t pos; /* Buffer cursor */
size_t len; /* Buffer length */
size_t maxbuf; /* Max length of unused buffer */
redisReadTask rstack[9];
int ridx; /* Index of current read task */
void *reply; /* Temporary reply pointer */
redisReplyObjectFunctions *fn;
void *privdata;
} redisReader;
/* Public API for the protocol parser. */
redisReader *redisReaderCreate(void);
void redisReaderFree(redisReader *r);
int redisReaderFeed(redisReader *r, const char *buf, size_t len);
int redisReaderGetReply(redisReader *r, void **reply);
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呵呵，打包和解包看来不是一个简单的函数搞定的，就原谅自己的眼拙了。哈哈。
实战演习
来一个简单的例子（demo.c），假设实例里面的函数
int asyncFrameWork(const uint8_t* sendBuf, int sendBufLen, uint8_t* recvBuf, int* recvBufLen);
就是公司高大上的异步服务器框架了啊。（汗颜一下。。。）
或者把这个asyncFrameWork替换为目前很前沿的微线程（协程）技术，那性能也是相当高的。
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#include "hiredis.h"
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <unistd.h>
#include <stdint.h>
int asyncFrameWork(const uint8_t* sendBuf, int sendBufLen, uint8_t* recvBuf, int* recvBufLen)
{
if (sendBuf == NULL || recvBuf == NULL || sendBufLen < 1 || *recvBufLen < 1) {
printf("asyncFrameWork param error.\n");
return -1;
}
int fd = socket(AF_INET, SOCK_STREAM, 0);
if (fd < 0) {
printf("socket error : %d\n", errno);
return -1;
}
struct sockaddr_in addr;
memset(&addr, 0x00, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(6379);
addr.sin_addr.s_addr = inet_addr("127.0.0.1");
int ret = connect(fd, (struct sockaddr*)&addr, sizeof(addr));
if (ret) {
printf("connect error : %d\n", errno);
close(fd);
return -2;
}
ret = send(fd, sendBuf, sendBufLen, 0);
if (ret < 0) {
printf("send error : %d\n", errno);
close(fd);
return -3;
}
ret = recv(fd, recvBuf, *recvBufLen, 0);
if (ret <= 0) {
printf("recv error : %d\n", errno);
close(fd);
return -4;
}
*recvBufLen = ret;
printf("asyncFrameWork recv len = %d\n", ret);
close(fd);
return 0;
}
int setCmd(const char* key, const char* value)
{
char* cmdBuf = NULL;
int len = 0;
len = redisFormatCommand(&cmdBuf, "SET %s %s", key, value);
if (len < 0) {
printf("redisFormatCommand error! len = %d\n", len);
return -1;
}
printf("redisFormatCommand result: len = %d, cmdBuf = %s\n", len, cmdBuf);
int ret = 0;
char recvBuf[1024] = {0};
int recvBufLen = sizeof(recvBuf);
ret = asyncFrameWork((const uint8_t*)cmdBuf, len, (uint8_t*)recvBuf, &recvBufLen);
if (ret) {
printf("asyncFrameWork error:%d!\n", ret);
free(cmdBuf);
cmdBuf = NULL;
return -2;
}
printf("asyncFrameWork return : recvBuf = %s, recvBufLen = %d\n", recvBuf, recvBufLen);
free(cmdBuf);
cmdBuf = NULL;
redisReader *reader = NULL;
void *reply = NULL;
reader = redisReaderCreate();
if (reader == NULL) {
printf("redisReaderCreate error!\n");
return -3;
}
redisReaderFeed(reader, recvBuf, recvBufLen);
ret = redisReaderGetReply(reader, &reply);
if (ret != REDIS_OK) {
printf("redisReaderGetReply error:%d!\n", ret);
redisReaderFree(reader);
reader = NULL;
return -4;
}
if (reply == NULL) {
printf("redisReply is NULL!\n");
redisReaderFree(reader);
reader = NULL;
return -5;
}
printf("redisReader get reply : %d\n", *((int*)reply));
struct redisReply *r = (struct redisReply*)reply;
printf("r->type = %d\n", r->type);
if (REDIS_REPLY_ERROR == r->type) {
printf("redisReply return REDIS_REPLY_ERROR!\n");
freeReplyObject(reply);
redisReaderFree(reader);
reader = NULL;
return -6;
}
if (REDIS_REPLY_STATUS != r->type) {
printf("redisReply return is't REDIS_REPLY_STATUS!\n");
freeReplyObject(reply);
redisReaderFree(reader);
reader = NULL;
return -7;
}
printf("-------------------------------------\n");
if (r->integer == REDIS_OK)
printf("set key(%s) OK\n", key);
else
printf("set key(%s) FAIL\n", key);
printf("-------------------------------------\n");
freeReplyObject(reply);
redisReaderFree(reader);
return 0;
}
int getCmd(const char* key)
{
char* cmdBuf = NULL;
int len = 0;
len = redisFormatCommand(&cmdBuf, "GET %s", key);
if (len < 0) {
printf("redisFormatCommand error! len = %d\n", len);
return -1;
}
printf("redisFormatCommand result: len = %d, cmdBuf = %s\n", len, cmdBuf);
int ret = 0;
char recvBuf[1024] = {0};
int recvBufLen = sizeof(recvBuf);
ret = asyncFrameWork((const uint8_t*)cmdBuf, len, (uint8_t*)recvBuf, &recvBufLen);
if (ret) {
printf("asyncFrameWork error:%d!\n", ret);
free(cmdBuf);
cmdBuf = NULL;
return -2;
}
printf("asyncFrameWork return : recvBuf = %s, recvBufLen = %d\n", recvBuf, recvBufLen);
free(cmdBuf);
cmdBuf = NULL;
redisReader *reader = NULL;
void *reply = NULL;
reader = redisReaderCreate();
if (reader == NULL) {
printf("redisReaderCreate error!\n");
return -3;
}
redisReaderFeed(reader, recvBuf, recvBufLen);
ret = redisReaderGetReply(reader, &reply);
if (ret != REDIS_OK) {
printf("redisReaderGetReply error:%d!\n", ret);
redisReaderFree(reader);
reader = NULL;
return -4;
}
if (reply == NULL) {
printf("redisReply is NULL!\n");
redisReaderFree(reader);
reader = NULL;
return -5;
}
printf("redisReader get reply : %d\n", *((int*)reply));
struct redisReply *r = (struct redisReply*)reply;
printf("r->type = %d\n", r->type);
if (REDIS_REPLY_ERROR == r->type) {
printf("redisReply return REDIS_REPLY_ERROR!\n");
freeReplyObject(reply);
redisReaderFree(reader);
reader = NULL;
return -6;
}
if (REDIS_REPLY_STRING != r->type) {
if (REDIS_REPLY_NIL == r->type) {
printf("-------------------------------------\n");
printf("key(%s) not exists!\n", key);
printf("-------------------------------------\n");
}
else
printf("redisReply return is't REDIS_REPLY_STRING!\n");
freeReplyObject(reply);
redisReaderFree(reader);
reader = NULL;
return -7;
}
printf("r->len = %d\n", r->len);
printf("r->str = %s\n", r->str);
printf("-------------------------------------\n");
printf("key(%s), value=(%s)\n", key, r->str);
printf("-------------------------------------\n");
freeReplyObject(reply);
redisReaderFree(reader);
return 0;
}
int main(int argc, char** argv)
{
setCmd("company", "leoox");
getCmd("company..");
getCmd("company");
return 0;
}
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编译
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gcc -o demo -I/home/leoox/soft/hiredis-master demo.c /home/leoox/soft/hiredis-master/libhiredis.a
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执行
用valgrind执行一下，看结果是否正确的同时，也顺便看看是否有内存泄露。
[amcool@leoox redisDemo]$ valgrind –leak-check=full –tool=memcheck ./demo
==3868== Memcheck, a memory error detector.
==3868== Copyright (C) 2002-2006, and GNU GPL’d, by Julian Seward et al.
==3868== Using LibVEX rev 1658, a library for dynamic binary translation.
==3868== Copyright (C) 2004-2006, and GNU GPL’d, by OpenWorks LLP.
==3868== Using valgrind-3.2.1, a dynamic binary instrumentation framework.
==3868== Copyright (C) 2000-2006, and GNU GPL’d, by Julian Seward et al.
==3868== For more details, rerun with: -v
==3868==
redisFormatCommand result: len = 37, cmdBuf = *3
$3
SET
$7
company
$5
leoox
asyncFrameWork recv len = 5
asyncFrameWork return : recvBuf = +OK
, recvBufLen = 5
redisReader get reply : 5
r->type = 5
————————————-
set key(company) OK
————————————-
redisFormatCommand result: len = 28, cmdBuf = *2
$3
GET
$9
company..
asyncFrameWork recv len = 5
asyncFrameWork return : recvBuf = $-1
, recvBufLen = 5
redisReader get reply : 4
r->type = 4
————————————-
key(company..) not exists!
————————————-
redisFormatCommand result: len = 26, cmdBuf = *2
$3
GET
$7
company
asyncFrameWork recv len = 11
asyncFrameWork return : recvBuf = $5
leoox
, recvBufLen = 11
redisReader get reply : 1
r->type = 1
r->len = 5
r->str = leoox
————————————-
key(company), value=(leoox)
————————————-
==3868==
==3868== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 5 from 1)
==3868== malloc/free: in use at exit: 0 bytes in 0 blocks.
==3868== malloc/free: 41 allocs, 41 frees, 2,352 bytes allocated.
==3868== For counts of detected errors, rerun with: -v
==3868== All heap blocks were freed — no leaks are possible.
结果正确，并且没有内存泄露。perfect！哦，圣诞过完了，那提前说元旦快乐，新的一年要任性！